cash discount
US /kæʃ ˈdɪskaʊnt/
UK /kæʃ ˈdɪskaʊnt/

1.
a reduction in the price of goods or services allowed to a buyer in return for prompt payment
:
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We offer a 2% cash discount for payments made within 10 days.
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The store gives a cash discount if you pay with debit card instead of credit card.